FUNGI, BLACK MOLD 275 



are very numerous and float readily in the air, so that if a piece of 

 bread or cooked potato is left exposed in a room or out of doors 

 for a day or less, and then covered in a pan with some moist 

 paper, in a few days the mold will appear. The mycelium is 

 white and forms an abundant growth of threads forming the 

 white glistening mat which spreads over the bread or other 

 substances. 



416. Asexual reproduction. The mycelium is the vegetative 

 or growing stage of the fungus. Within a day or so after the 

 mycelium begins to form, asexual reproduction begins and at 

 the same time the mycelium continues to spread. Here and 

 there upon a thread of myce- 

 lium, erect hyphae arise in tufts 

 of three to five or more (fig. 219). 

 The ends of these branches be- 

 come enlarged into a rounded 

 body, the spore case or sporan- 

 gium, and the protoplasm is 

 separated from that of the stalk, 

 or sporophore (sometimes called 

 sporangiophore), by an arched 



Wall, the COlumdla. At maturity extending from an older group. 



the sporangium wall disintegrates so that the spores are 

 easily set free. The columella is often very large and might 

 be mistaken for the sporangium after the spores are scattered. 

 It sometimes collapses as shown in fig. 220. At the base of 

 the clusters of sporophores is a tuft of delicate, branched, 

 rootlet-like threads called rhizoids. These as well as the 

 sporophores become blackish in color. The larger number of 

 these clusters of sporophores are borne at intervals on distinct 

 creeping hyphae, which rise into the air and then touch the sub- 

 stratum here and there like the stolon of the strawberry vine, or 

 the leaf of the walking fern, developing a cluster of sporophores 

 at each point of contact. These stolon-like hyphae will spread 

 off from the bread onto the sides of the vessel. Because of this 

 peculiar stolon-like hypha this mold is sometimes called the stolon 



